Most conventional cameras use lenses to focus light on image planes to form bright and sharp images. In spite of the desirable features that lenses provide, lenses constrain the mapping from the scene to the image. For example, lens cameras severely restrict the geometry and photometry of the imaging process. As a result, conventional video cameras provide limited control over their imaging properties. This has a direct implication on the way computer vision systems are designed in terms of sensing and algorithms.
FIG. 1a is a cross-sectional view illustrating a conventional ideal lens camera 100. As shown, lens 101 integrates light 109 emanating from a point 111a in the scene 107 on the plane 105 in focus to a corresponding point 111b on the image detector 103. Therefore, lens 101 focuses plane 105 to the plane of image detector 103. Without moving lens 101 and/or image detector 103, the viewing direction and the focus of this lens camera cannot be changed. Motors (e.g., pan-tilt motors) can be used to move lens 101 and/or image detector 103, however, motors are limited by mechanical constraints and produce motion blur. In addition, this camera 100 can only acquire an image of an entire field of view together and is constrained to distribute the limited resolution of the detector 103 uniformly over an entire field of view.
In recent works, cameras that are more flexibly controllable were proposed. One proposed camera includes lenses and an array of micro-mirrors. By controlling the orientations of the micro-mirrors, pixel-wise multiplications in the optics and instantaneous changes of viewing directions can be performed. In another case, a camera with a lens and a light attenuator was proposed, which can also perform pixel-wise multiplications. These proposed cameras, while highly controllable, use one or more lens to focus a scene on an image detector.
Instead of using lenses, conventional pinhole cameras use small apertures for light collection. Conventional pinhole cameras are capable of acquiring an image of a wide field of view without incurring geometric distortions. However, conventional pinhole cameras also suffer from the kinds of inflexibility facing lens cameras.